"Custom" build tab

So earlier I'm building some space themed buildings and was continually switching between the "Building" and "Scenery" tabs. It made me realize that it would be amazing to have what I'll call a "build palette," or more simply, a "custom" tab. Basically a tab that I can add pieces to myself so I don't have to go back and forth between tabs and waste time, like a painter's palette. So I could add the walls, decorations, scenery, and paths to one place and not have to constantly switch. When you're done with the building you could clear the tab and start adding things for the next building. You could also make it so when the user is in this tab, they can edit across all tabs. No more having to switch to the "Paths" tab to delete a path that's in the way, only to switch immediately back. Finally, kind of a similar idea but I'll toss it in also: a "Contains" tab. When you click on a building the "Contains" tab will show you all the pieces used within the building, and the tab can be used if you decide to expand the building.

What do you guys think?